The 2.1.0 system update was released on March 27, 2017. This update was released for all regions.
Security flaws fixed: yes.
Change-log
This is the official changelog from Nintendo regarding this update:
Improvements Included in Version 2.1.0
- General system stability improvements to enhance the user's experience
System Titles
It's unknown exactly what titles were updated.
Browser
Multiple browser vulns were fixed, see also here for v2.1 browser details.